Spectral curves of non-hermitian hamiltonians

Recent analytical and numerical work have shown that the spectrum of the random non-hermitian Hamiltonian on a ring which models the physics of vortex line pinning in superconductors is one dimensional. In the maximally non-hermitian limit, we give a simple "one-line" proof of this feature. We then study the spectral curves for various distributions of the random site energies. We find that a critical transition occurs when the average of the logarithm of the random site energy squared vanishes. For a large class of probability distributions of the site energies, we find that as the randomness increases the energy E-* at which the localization-delocalization transition occurs increases, reaches a maximum, and then decreases. The Cauchy distribution studied previously in the literature does not have this generic behavior. We determine gamma(c1), the critical value of the randomness at which "wings" first appear in the energy spectrum. For distributions, such as Cauchy, with infinitely long tails, we show that gamma(c1) = 0(+). We determine the density of eigenvalues on the wings for any probability distribution. We show that the localization length on the wings diverge generically as L(E) similar to 1/\E - E-*\ as E approaches E-*. These results are all obtained in the maximally non-hermitian limit but for a generic class of probability distributions of the random site energies, (C) 1999 Elsevier Science B.V. All rights reserved.